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Further Notes on the Methods of Examining and Chemistry of Fixed Oils. By A. H. ALLEN (J. Soc. Chem. Ind., 5, 65–72, and 282-283).—Specific Gravity of Oils.-A convenient instrument for ascertaining the density of fixed oils is Westphal's hydrostatic balance. A counterpoised thermometer suspended from a piece of thin platinum wire is attached to one end of a graduated lever. On immersing the thermometer in a liquid, it loses a certain weight. The equilibrium is restored by hanging on the lever a series of riders, which are adjusted in weight so as to make the reading very simple. As the employment of a thermometer as a plummet renders the instrument unsuited for determinations of density at 100°, or other high temperature, the author substitutes in such cases a plummet of thick glass rod. For the determination of the density of fats the author some time ago recommended the use of a Sprengel tube, and urged that the density should be taken at the boiling point of water. In all cases, however, where there is sufficient substance at disposal, the Sprengel tube has been abandoned in favour of the plummet.

Coefficients of Expansion of Oils.—A series of tables illustrating the rates of expansion of fats and oils are given, showing (1) that the rates of expansion of the fluid fixed oils are not sufficiently different to be of any value for their recognition; (2) that of the fluid fixed oils examined (sperm oil, bottle-nose oil, whale oil, porpoise oil, seal oil, menhaden oil, neats-foot oil, lard oil, olive oil, arachis oil, rape oil, sesamé oil, cotton-seed oil, niger-seed oil, linseed oil, and castor oil) all with the exception of whale oil expand sensibly equally for the same increase of temperature; and (3) that with the exception of whale oil the correction in density for the fluid fixed oils examined may safely be taken at 0.64 for 1° C. (water at 15.5° = 1000).

Viscosity of Oils.-The author is of opinion that Redwood's new form of viscosimeter bids fair to become the recognised standard instrument of the future. For many purposes, however, and especially as a convenient test by oil merchants, the following instrument is likely to grow in favour. It consists of a simple arrangement by which a small paddle-wheel (actuated by a falling weight) is caused to revolve in the sample of oil maintained at a definite temperature by an outer vessel of water. The manipulation is very simple, and the results expressed by the number of seconds required by the weight to fall through a given space are very constant.

Bromine and Iodine Absorptions of Oils.-In order to facilitate the comparison between the results of Mills (ibid., 2, 435, and 3, 366) and Hübl (Abstr., 1884, 1435), the author has multiplied the bromine 127 absorptions obtained by Mills by so as to obtain the equivalent 9 80 iodine absorptions, and has compared the results with the experimental numbers for iodine absorptions obtained by Hübl. figures which are tabulated in the original paper indicate that the drying oils (containing linoleic acid) assimilate the largest proportions of the haloïds, and their capacity in this respect might probably be employed as a measure of their drying properties. The fish liver oils, however, fully equal the vegetable oils in their assimilating power for haloïds. Hübl's results in the main confirm those of Mills.

The

Valenta's Acetic Acid Test.-The author has tried this method (Abstr., 1884, 1078) on a number of oils and finds that a slight variation in the strength or proportion of the acid employed is not of importance, and that the temperature at which turbidity occurs with any particular specimen is readily observed and fairly constant. Concordant results have also been obtained from several samples of butter, and it appears probable that further experience may prove the method to afford a simple means of distinguishing butter from butterine.

Determination of Glycerol.-The difficulties attending the determination of the glycerol produced by the saponification of fixed oils have recently been overcome by a method originally suggested by Wanklyn and Fox (Abstr., 1886, 395), and perfected by Benedikt and Zsigmondy. It depends on the saponification of the oil, and oxidation of the glycerol thus formed by potassium permanganate in alkaline solution, with formation of oxalic acid, carbonic anhydride, and water. The excess of permanganate is then destroyed by a sulphite, the solution filtered, the filtrate acidified with acetic acid, and precipitated with a calcium salt. As the precipitate contains calcium sulphate and silicic acid in addition to calcium oxalate, the amount of oxalic acid is determined either by titration of the precipitate with permanganate in acid solution, or by estimating the alkalinity of the ignited precipitate. For the determination of glycerol in fats, the author recommends modifying the method in the following manner :-5 grams of the sample of fixed oil is placed in a six-ounce bottle, together with a solution of 2 grams of caustic potash in 12 c.c. of water. The bottle is securely closed and heated in a water-oven or in boiling water for 8 or 10 hours, the contents being frequently agitated. When the product is perfectly homogeneous and all oily globules have disappeared, the bottle is opened, and the soap diluted with hot water, when a perfectly clear solution should be obtained, except in cases of sperm oil, wax, and other substances yielding insoluble alcohols on saponification. The soap solution is then treated with a moderate excess of acid in the usual way, and the liberated fatty acids are separated from the aqueous liquid containing the glycerol, which latter is then ready for oxidation with alkaline permanganate as above described. D. B.

Maumené's Test for Oils. By C. J. ELLIS (J. Soc. Chem. Ind., 5, 150-152 and 361-362).—The author has made some experiments with the view of extending the application of Maumené's test to drying oils and fish oils, to which it cannot be directly applied without some slight modification, owing to the violent action which ensues when these oils are mixed with concentrated sulphuric acid. To overcome this difficulty it was found necessary to mix with a drying or fish oil some liquid which will moderate the action of the acid on the oil. The author employed a mineral lubricating oil of 0.915 sp. gr. for this purpose, and as on mixing sulphuric acid with such an oil a certain increase of temperature takes place, it is necessary to determile the rise due to each gram of the mineral oil. To accelerate the action of sulphuric acid on the mineral oil, a certain proportion of

colza oil was added, for which the standard number, when not mixed, was accurately determined and found to be 55.8°. Contrary to expectation, it was found that the smaller the quantity of mineral oil in the mixture the greater is the value representing the rise due to each gram of the mineral oil, providing the rise due to each gram of the vegetable oil remains constant whatever the mixture. To calculate the rise in temperature due to each gram of the mineral oil the following formula is employed:-y = a + bx, in which y represents the rise in temperature due to each gram of mineral oil, x is the fraction of the mixture consisting of mineral oil, and a and b are constants depending on the conditions of the experiment and the particular mineral oil employed.

In order to obtain the most concordant and trustworthy results, the maximum temperature attained should not exceed 60°, and it is for this reason that the author prefers the use of a mineral oil as the retarding reagent.

D. B.

Employment of Congo-red in Titrating Aniline. By P. JULIUS (Chem. Ind., 9, 109-110).-Congo-red, the compound of tetrazodiphenyl with naphtholsulphonic acids, is turned blue by acids, and recovers its red colour with an excess of alkali. When used as an indicator in titrating aniline or its homologues with a mineral acid, the point is taken at which a bluish-violet, not changed by small further additions of acid, is produced. A much larger excess is required to produce a pure blue. The results do not vary more than 0.2 per cent. from the theoretical numbers. M. J. S.

Hüfner's Method of Estimating Urea. By E. PFLÜGER and K. BOHLAND (Pflüger's Archiv, 39, 1-17).-Pflüger and Schenk previously proved (ibid., 38, 325) that Hüfner's method of estimating the nitrogen in urine gave results which were too low and variable to found a calculation of the total nitrogen on. Owing to the improvement made in Bunsen's method, the authors have been able to ascertain whether Hüfner's method was sufficiently accurate for the determination of urea only. They find that the results are always too high and also very variable. The variation ranges from 1 per cent. to 10 per cent., and does not therefore admit of compensation.

J. P. L.

Estimation of Urea in Human Urine with Sodium Hypo. bromite. By E. PFLÜGER and K. BOHLAND (Pflüger's Archiv, 39, 143-158).-Pflüger's new method of estimating urea by hypobromite (Pflüger's Archiv, 38, 503) can be applied to the estimation of urea in human urine provided the nitrogenous extractives are first removed. For this purpose, a given volume of urine acidified with hydrochloric acid (1 of acid to 10 of urine) is precipitated with sufficient phosphotungstic acid to ensure the separation of all the extractives, the mixture made up to a known volume, and allowed to remain 24 hours at least previous to filtration. The acid filtrate is carefully neutralised with powdered lime, and again filtered through a dry filter.

Great stress is laid on the use of pure soda and bromine for the

preparation of the hypobromite. The mean error of several analyses of urine by this process was + 1.3 per cent. J. P. L.

Qualitative Tests for the Dyes Found in Commerce. By O. N. WITT (Chem. Ind., 9, 1—7).-A table of reactions for the identification of about 80 artificial colouring matters taken singly. Many commercial dyes are mixtures: in this case, the powder strewn upon wet filter-paper or colourless sulphuric acid will generally give streaks of more than one colour. Where the mixture is more intimate a solution must be made, and the colouring matters withdrawn fractionally by dyeing small pellets of wool or silk in it. The principal adulterant for azo-dyes is sodium sulphate. It is best detected after precipitating the colour by pure sodium chloride. M. J. S.

Detection of Artificially Coloured Red Wine (Claret). By J. HERZ (Chem. Zeit., 10, 968—969; 998).-To 30-50 c.c. of the wine, or if the quantity of colouring matter in the wine is small, 100 c.c. concentrated to 30 c.c., 20-30 c.c. of a saturated solution of magnesinm sulphate, and 10-20 c.c. of soda solution are added, stirring well; if necessary the treatment is repeated until the liquid is colourless, or nearly so. The filtrate is made acid with dilute sulphuric acid (1:3), and if sulphonic acid colours are present the red colour reappears. The most commonly used member of this group, acid-magenta (rosanilinesulphonic acid), yields a violet-red solution, and can be estimated by comparing the tint with magenta solutions of known strength. One mgram. of magenta per litre can be distinctly detected in 30 c.c. of wine without previous concentration. When archil (orseille) colours are present, the filtrate is bluish, and when made acid turns a litmus-red colour. To test for magenta under such circumstances, Blarez' method of shaking with lead dioxide is used; this destroys the orseille and natural colour. Cazeneuve's method is not recommended. To test for other colours in the magnesium hydroxide precipitate, the gelatinous mass is stirred up with hot water, allowed to settle, and the liquid decanted off. If only the natural colour of the wine is present, or bilberry has been used, this liquid is yellow-brown; if archil has been used, dark-violet; if ponceau, onion or ponceau red; if cassissine, pale-red or dark-yellow; if vinicoline bordelaise, a yellow-red to yellow-brown liquid, which when poured on sulphuric acid gives a violet ring. By shaking the coloured liquid with amyl alcohol, ponceau yields an onion-red residue ; vinicoline, a dark-brown one; cussissine, a dirty-green, violet at the edge, turned yellow by strong hydrochloric acid. The precipitate is a dark-grey or brownish-grey colour when the natural or vegetable colours only are present; with archil, it is violet; with magenta (acid or ordinary), dirty white; with cassissine, dirty yellow-brown; with vinicoline, crimson-red. The precipitate is mixed with sand, dried, and extracted with ether; the extract contains any ordinary magenta which can be identified in the usual manner by dyeing wool, or cassissine which dyes wool red-brown and leaves a yellow-brown residue in the dish. The dyed wool becomes yellow when treated with strong hydrochloric acid and colourless with ammonia. When

wine is shaken with amyl alcohol, and the coloured extract evaporated, the residue, if it contains the substances named, behaves in the manner described below:

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whilst the wine after extraction is cherry-red with ordinary magenta, violet-red with acid-magenta, dark-cherry with Bordeaux, vellow-red with ponceau. Wine coloured with magenta produces a violet froth. The detection of vegetable colouring matters in presence of the natural colour of wine or otherwise is a matter of great difficulty, and most of the known methods are ineffectual; it is, however, effected by the author with comparative facility in the following manner: -10 to 15 c.c. of wine is shaken with 5 c.c. of a saturated solution of tartar emetic, and then examined by reflected and transmitted light either at once or, if no immediate change has taken place, after some time. This treatment produces with genuine red wine always a cherry-red colour, and with other substances as follows:-Red-poppy (Papaver rhaus), dark cherry-red; cherry, violet; commercial elder colouring matter, red-violet; bilberry (Vaccin. myrtill), blue-violet; privet-berry, pure violet. White wines artificially coloured, and red wines mixed with artificial colours have been successfully examined in this manner; in the latter case the wine some time after treatment is compared with a genuine red wine to distinguish more readily the change of colour. Old solutions of privet do not give the colour change. Sodium hydrogen carbonate produces with pure wine, brown-red; with wine. coloured with pure elderberry, grey-violet; and with bilberry, browngreen. Tartar emetic appears to form an antimony lake with the colouring matters. With practice, all the above-mentioned colours can be detected in 30-50 c.c. of wine. In the subsequent communication (loc. cit., 998), the author acknowledges the priority of Ambühl and Elsner's recommendation of the use of tartar emetic for the purpose in question. They, however, recommend hot solutions; the author finds cold better. Fermented bilberries give the violet colour even better than unfermented berries, especially when fresh, inasmuch as oxidation interferes with the delicacy after a time. The distinctness of this colour is increased by diluting the wine. D. A. L.

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